The present disclosure is related to downhole tools used in the oil and gas industry and, in particular, to a release tool used to separate portions of a tool string.
Hydrocarbons are typically produced from wellbores drilled from the Earth's surface through a variety of producing and non-producing subterranean zones. The wellbore may be drilled substantially vertically or may be drilled as an offset well that has some amount of horizontal displacement from the surface entry point. A variety of servicing operations may be performed in the wellbore after it has been drilled and completed by lowering different kinds of downhole tools into the wellbore. For example, a tool string containing measuring instruments are commonly lowered into the wellbore to obtain various downhole measurements, such as bottom hole pressure and temperature. Various sampling devices are also commonly lowered into the wellbore in the tool string to obtain fluid samples at various target zones of the subterranean formation in order to determine the exact composition of the formation fluids of interest.
Such servicing operations are typically undertaken by lowering the tool string and its various downhole tools into the wellbore on a tension member conveyance, such as wireline or slickline. After the wellbore servicing operation is completed, the downhole tool is withdrawn from the wellbore and the slickline is re-coiled back onto an adjacent wire spool or drum. During its ascent to the surface, the tool string can sometimes become stuck due to differential sticking, key seating, hole sloughing, debris lodged in the wellbore, and other common wellbore conditions. In such situations, the tool string can oftentimes be freed through the application of ordinary tensile or compressive forces delivered to the tool string from the surface.
In other situations, however, the conveyance line must be severed from the tool string by introducing a cutting tool into the wellbore. The cutting tool is typically attached to the conveyance and allowed to slide down the conveyance as it is dropped from the surface. Upon contacting or striking the top of the tool string, the cutting tool may be configured to cut the conveyance such that the upper portions of the conveyance line may be retrieved to the surface. Oftentimes the cutting tool prematurely cuts the conveyance upon striking a restriction at some distance above the tool string within the wellbore. This will often leave a long length of conveyance line remaining above the tool string that requires fishing operations that could result in considerable added expense. The fishing job could very well require coiled tubing or tubing fishing which, in addition to service costs, could result in days or weeks of lost rig time and lost production.